The present subject matter relates generally to wind turbines and particularly to rotor blade deflection. More particularly, the present subject matter relates to a rotor blade configured to address rotor blade deflection during operation of a wind turbine.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size and capacity of wind turbines. One such modification has been to increase the length of the rotor blades. However, as is generally understood, deflection of a rotor blade is a function of blade length, along with wind speed, turbine operating states and blade stiffness. Thus, longer rotor blades may be subject to increased deflection forces, particularly when a wind turbine is operating in high-speed wind conditions. These increased deflection forces not only produce fatigue on the rotor blades and other wind turbine components but may also increase the risk of the rotor blades striking the tower. A tower strike can significantly damage a rotor blade and the tower and, in some instances, can even bring down the entire wind turbine. Accordingly, a tower strike may result in considerable downtime to repair or replace damaged components.
Known wind turbine systems commonly determine rotor blade deflection by utilizing external sensors, which are typically mounted on the rotor blades or on the tower. These sensors are designed to sense rotor blade operating conditions (e.g. blade strain, blade acceleration or blade velocity) to enable blade deflection to be inferred or calculated. In other instances, the sensors are designed to sense the distance of the rotor blade from the tower during operation. Action may be taken as a result of the sensed data to minimize the risk of the rotor blade impacting the tower. However, maintaining the sensors can be very costly and calibrating such sensors can be quite complex and time consuming. Moreover, since the sensors must be calibrated frequently, there is a concern with regard to the reliability of data transmitted from the sensors over an extended period of time.
Accordingly, there is a need for a means to address wind rotor blade deflection without the excessive complexity and costs of calculating deflection during operation.